ML25119A268
| ML25119A268 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 04/29/2025 |
| From: | Fleming J Holtec Decommissioning International |
| To: | Document Control Desk, Office of Nuclear Material Safety and Safeguards |
| Shared Package | |
| ML25119A267 | List:
|
| References | |
| HDI-OC-25-017 | |
| Download: ML25119A268 (1) | |
Text
HDI-OC-25-017 Page 1 of 4 10 CFR 50.90 10 CFR 50.91 April 29, 2025 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Oyster Creek Nuclear Generating Station Renewed Facility Operating License No. DPR-16 NRC Docket No. 50-219 and 72-15
Subject:
Holtec Decommissioning Internationals response to Oyster Creek Nuclear Generating Station License Termination Plan Request for Supplemental Information
Reference:
[1]
Letter from Holtec Decommissioning International (HDI) to Nuclear Regulatory Commission (USNRC) - License Amendment Request to Revise Oyster Creek Nuclear Generating Station Renewed Facility Operating License to Add License Condition 2.C.(18) to Include License Termination Plan Requirements, August 1,2024, (ML24214A037).
[2]
Letter from USNRC (ML24269A046) with Enclosure 1(ML24269A049) to HDI - Oyster Creek Nuclear Generating Station - License Termination Plan Acceptance Review Request for Supplemental Information, October 4, 2024
[3]
Letter from USNRC (ML24284A197) to HDI - Oyster Creek Nuclear Generating Station - License Termination Plan Acceptance Review Request for Supplemental Information - Revision to Enclosures (ML24284A196), October 10, 2024
[4]
HDIs Response to LTP Request for Supplemental Information (RSI) numbers 10, 11, 12 and 13, March 26,2025 (ML25086A156)
On August 1, 2024 Holtec Decommissioning International, LLC (HDI) requested approval of a proposed amendment to the Renewed Facility Operating License DPR-16 for Oyster Creek Nuclear Generating Station (OCNGS) to include License Termination Plan (LTP) Requirements (Reference 1).
On October 4, 2024, the NRC issued a request for supplemental information (RSI) required to complete the acceptance review of the proposed License Termination Plan by March 31, 2025 (Reference 2).
On October 10, 2024, the NRC modified some of the requests (Reference 3).
HDI-OC-25-017 Page 2 of 4 On March 26, 2025, HDI submitted responses to environmental RSI numbers 10 through 13 (Reference 4).
Holtec Decommissioning International (HDI) hereby submits responses for RSI number 1 through 9 as requested by the NRC related to the acceptance review of Oyster Creeks License Termination Plan (LTP) Revision 0 (Reference 3).
The OCNGS LTP Revision 0 has been updated to Revision 1 to incorporate changes resulting from RSI responses. The additional characterization and information collected as part of the RSI responses has been incorporated into Oyster Creek LTP Revision 1.The portions of the LTP that have been updated are marked with revision bars. is the response to the remaining RSIs in Reference [3] (RSI numbers 1 through 9).
The LTP and supporting technical documents described below will be submitted separately:, Oyster Creek Nuclear Generating Station License Termination Plan, Revision 1, April 2025., OCNGS Historical Site Assessment, Revision 2, November 2021, TBD 20-6002-1362 Revision 1 Radionuclide Selection for DCGL Development Oyster Creek Station Site Characterization Project, January 17, 2022, Oyster Creek Generating Station Radiological Characterization Report Revision 1, April 24, 2023, Oyster Creek Nuclear Generating Station Below Grade Structures Radiological Characterization Report Revision 1, March 2024, Technical Support Document 25-015 Revision 0, Building Surface DCGL Values - Oyster Creek [Supersedes ENG-OCS-002 Revision 1, RESRAD-Build Input Parameter Sensitivity Analysis - OCS, March 6, 2024], ENG-OCS-004 Revision 0, RESRAD Building Surface DCGL Values Oyster Creek, April 12, 2022, ENG-OCS-006 Revision: 1, Area Factors for Use with Oyster Creek DCGL Values for Buildings/Structures, April 14, 2022 0, ENG-OCS-007 Revision 0, RESRAD-Onsite Probabilistic Analysis - Industrial Use Scenario Oyster Creek Station, July 25, 2023 1, ENG-OCS-008 Revision: 0, Derived Concentration Guideline Levels Values for Soil - Industrial Use Scenario Oyster Creek, July 26, 2023 2, ENG-OCS-009 Revision: 0, Area Factors for Soil - Industrial Use Scenario, August 4, 2022
HDI-OC-25-017 Page 3 of 4 3, ENG-OCS-012 Revision: 0, Basement Fill Model Probabilistic Analysis for Instantaneous Release Scenario Assuming Industrial Use Exposure Pathways Oyster Creek, November 1, 2023 4, ENG-OCS-013 Revision: 1, Basement Fill Model: Calculation of DCGLW/F Values Assuming Industrial Use Scenario Exposure Pathways Oyster Creek Station, March 6, 2024 5, ENG-OCS-014 Revision: 0, Basement Fill Model: Probabilistic Analysis for Embedded Pipes Scenario Oyster Creek Station, January 2024 6, ENG-OCS-015 Revision: 1, Basement Fill Model: Calculation of Embedded Pipe DCGL Values Oyster Creek Station, March 6, 2024 7, ENG-OCS-016 Revision: 0, Calculation of Buried Pipe DCGL Values Oyster Creek Station, February 20, 2024 8, TSD 25-032 Revision 0, Radionuclides of Concern in Support of the Oyster Creek Station License Termination Plan, April 4, 2025 [Supersedes Technical Basis Document No. 24-01-12-2888 Revision 1, Dose Contribution from Insignificant Radionuclides in the Oyster Creek Site-Specific Suite of Radiological Nuclides, February 14, 2024] 9, Technical Basis Document 24-108 Revision 1, Instrument Efficiency Determination for Use in Minimum Detectable Concentration Calculations in Support of the Final Status Surveys at OCNGS March 31, 2025 [Supersedes Revision 0] 0, Oyster Creek 100 Year Land Use Outlook - Categorization and Justification, GHD, February 9, 2024 1, Oyster Creek Hydrogeologic Investigation Report, September 8, 2022 2, TSD 24-055 Revision 0, Basement Fill Model: Probabilistic Analysis for Instantaneous Release Scenario Assuming Industrial Use Exposure Pathways 3, TSD 24-063 Revision 0, Basement Fill Model: Calculation of DCGLW/F Values Assuming Industrial Use Scenario Exposure Pathways 4, TSD 25-060 Revision 1, In Situ Object Counting System (ISOCS) as Applied to Final Status Survey at Oyster Creek Nuclear Generating Station, April 2, 2025
[Supersedes Revision 0] 5, TSD 24-062 Revision 1, OCNGS Structure Nuclide Fractions and Gross Activity DCGLs (DCGLGA), April 2, 2025 [Supersedes Revision 0] 6, TSD 24-081, Revision 0, Oyster Creek Groundwater Dose Calculation Methodology to Support the License Termination Plan, January 23, 2025 7, TSD 24-103 Revision 0, Distribution Coefficient (Kid) of Radionuclides in Soil Samples from the Oyster Creek Generating Station, March 27,2025
HDI-OC-25-017 Page 4 of 4 8, TSD 24-111 Revision 0, Surface/Sub Surface Characterization Survey Plan for the Oyster Creek Nuclear Generating Station, December 21, 2024 9, TSD 24-085 Revision 0, Probabilistic Dose Comparisons: Building Occupancy Scenario vs. Room Renovation Scenario, September 17, 2024 HDI will provide LTP Chapter 2 Reference 2-14, AMO Environmental Decisions March 2025 Letter to OCNGS RGPP Coordinator, 2024 Annual RGPP Monitoring Report Summary of Results and Conclusions on the HDI-NRC SharePoint site to facilitate NRC Staff review of the RSI responses.
HDI will also provide characterization results for NRC Staff review as specified in the attached RSI responses.
Should you have any questions or require any further information, please contact me at (856) 797-0900 x 3578.
I certify under penalty of perjury that the foregoing is true and correct. Executed on April 29, 2025.
Sincerely, Jean A. Fleming Vice President, Licensing and Regulatory Affairs Holtec International Response to Oyster Creek License Termination Plan Requests for Supplemental Information cc:
USNRC Regional Administrator, Region I USNRC Project Manager, NMSS - Oyster Creek Nuclear Generating Station USNRC Region I, Lead Inspector - Oyster Creek Nuclear Generating Station Assistant Commissioner, Air Quality, Energy and Sustainability, NJ DEP Principal Engineer, American Nuclear Insurers Assistant Director Radiation Protection Element, NJ Bureau of Nuclear Engineering Digitally signed by Jean A. Fleming DN: cn=Jean A. Fleming, o=Holtec Decommissioning International, LLC, ou=Regulatory and Environmental Affairs, email=J.Fleming@Holtec.com Date: 2025.04.29 13:46:24 -04'00' Jean A.
Fleming
HDI-OC-25-017 Response to OCNGS License Termination Plan Requests for Supplemental Information
1 RSI-1 Identify and describe the survey units within each area of the site, including the classification, area, and general information on surrounding survey units. Include maps with defined boundaries of the survey units, the scan and sample locations, and survey unit sizes.
Rationale:
The survey unit is the fundamental unit for demonstrating compliance with release criteria.
Planning, implementation, and data assessment are conducted for each survey unit. NUREG-
- 1575, Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM)
(ML003761445), Section 4.6, Identify Survey Units, recommends survey units should be limited in size based on classification, exposure pathway modeling assumptions, and site-specific conditions, and provides maximum survey unit sizes for structures and land areas.
Holtec Response In accordance with NUREG-1575, Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM), impacted areas are areas that have some potential for containing contaminated material and can be subdivided into Class 1, Class 2 or Class 3 areas. A site may be divided into survey units at any time before the final status survey. Dividing the site into survey units is critical only for the final status survey. Scoping, characterization, and remedial action support surveys may be performed without dividing the site into survey units.
The Oyster Creek Historical Site Assessment (HSA) conservatively concluded that the entirety of the licensed site was impacted by almost 50 years of plant operation. All areas and structures, systems and components (SSCs) were given a preliminary classification based on available survey data, process knowledge, and results of employee interviews. As stated in the HSA, the preliminary classification of an area or SSC may be revised between now and the time of site closure or license termination when additional characterization data becomes available.
The Oyster Creek Characterization Plan grouped the HSA locations of interest in nine areas and provided a matrix showing the relationship between the seventy-eight locations of interest described in the HSA and the nine areas described in the Characterization Plan.
Oyster Creek site characterization activities have provided a robust dataset that informs the initial classification of areas and helps determine the extent of remediation required. The current data offers a comprehensive understanding of the radiological profile across different site areas, ensuring that when survey unit boundaries are finalized during the Final Status Survey (FSS) phase, they will be based on accurate contamination profiles.
Survey unit boundaries will remain flexible throughout the decommissioning process, allowing adjustments to size and boundaries based on the final radiological conditions of the site. This phased approach aligns with MARSSIM guidelines (Section 4.6), ensuring that survey unit sizes reflect contamination variability and meet release criteria after remediation.
The proposed license conditions associated with the Oyster Creek License Termination plan include the following requirement:
Reclassification of survey areas, as described in MARSSIM, from a less to a more restrictive classification (e.g., from a Class 3 to a Class 2 area) may be done without prior NRC notification; however, reclassification to a less restrictive classification (Class 1 to Class 2 area) will require NRC notification at least 14 days prior to implementation.
2 Initial survey area boundaries have already been defined to guide remediation efforts, and estimates of survey unit numbers are included in Chapter 5 of the LTP. These estimates will be finalized based on each area's post-remediation condition. The final scan and sample locations will be determined after survey units are turned over to the FSS team, but current characterization data has identified areas with the highest contamination potential, which will be prioritized in FSS planning.
This flexible, phased approach ensures compliance with MARSSIM recommendations and will result in a final site survey that reflects the true radiological conditions at the time of license termination.
3 RSI-2 Site Characterization: Provide the radionuclide fractions, including characterization data used to derive them, to evaluate radionuclides of concern, insignificant contributors, surrogate ratios, relative ratios, and instrument efficiency.
Rationale:
The site characterization surveys are designed to provide a complete and unambiguous record of the radiological status of the site. To do so the characterization survey should determine the nature and horizontal and vertical extent of the residual radioactivity. An outcome of this survey is the determination of radionuclide fractions by area or media.
Holtec Response The initial Oyster Creek radiological characterization described in the Oyster Creek Generating Station Radiological Characterization Report and included as Enclosure 5 of the Oyster Creek License Termination Plan Revision 1 submittal focused on establishing a detailed radiological profile across the site, identifying areas requiring remediation, and classifying survey areas. This initial data collection was designed to guide the remediation strategy and ensure that areas of highest concern are prioritized for further assessment.
License Termination Plan Enclosure 6, Oyster Creek Nuclear Generating Station Below Grade Structures Radiological Characterization Report, documents the concrete characterization campaign performed to identify the nature and extent of radiological contamination in several Oyster Creek subgrade structures that will remain in place following decommissioning activities.
The analytical results from the concrete characterization campaign were used in the development of Technical Support Document (TSD) No.25-032, Radionuclides of Concern in Support of the Oyster Creek Station License Termination Plan, which is included with Oyster Creek License Termination Revision 1 submittal as Enclosure 18.
TSD 25-032 evaluates the results of concrete samples that were analyzed for the 21 radionuclides in the initial suite of radionuclides of concern (ROCs) identified in Technical Basis Document (TBD) 20-6002-1362, Radionuclide Selection for DCGL Development Oyster Creek Station Site Characterization Project, which is included with the Oyster Creek LTP Revision 1 submittal as. TSD 25-032 refines the initial ROCs into a final set of radionuclides of concern for use during final status survey (FSS). Radionuclide mixture fractions are established for the initial ROCs, and the results are used to eliminate some radionuclides as insignificant contributors (IC) to dose. Additionally, surrogate ratios were determined for the hard-to-detect ROCs.
A tabular summary of the concrete characterization results is presented in LTP Revision 1 Chapter
- 2. To facilitate Staff revies of the analytical results that support the determination of dose significant radionuclides and insignificant contributors, Oyster Creek will make the database containing the details of the analytical results, including minimum detectable activity and sensitivity results available for Staff review.
Going forward, continuing characterization will be performed to support remediation planning in areas of known contamination and expanded into additional locations as they become accessible.
As continuing characterization produces additional data during the decommissioning process, the determination of radionuclide fractions will be refined if necessary to accurately reflect the residual radiological conditions in full compliance with MARSSIM and NUREG-1757 guidance.
4 RSI-3, Oyster Creek Generating Station Site Radiological Characterization Report: For the samples selected for Hard-to-Detect (HTD) analysis, include the full suite of radionuclides in Table 2-7, Radionuclides of Concern, or provide justification for why a full suite of radionuclides was not provided.
Rationale:
NUREG-1700, Standard Review Plan for Evaluating Nuclear Power Reactor License Termination Plans, Revision 2 (ML18116A124), Section 2.5, Final Radiation Survey Plan, recommends the LTP include methods to address HTD radionuclides. For open land areas, Holtec Decommissioning International, LLC (HDI) selected quality control (QC) samples for analysis of HTD beta emitters (H-3, Sr-90, C-14, Fe-55, Ni-63, Tc-99). HDI included Pu-241 for the survey areas NPA (North Protected Area), SPA (South Protected Area), and the RCA (Radiologically Controlled Area), which HDI said have the highest potential for transuranic contamination. HDI excluded other HTDs listed in Table 2-7 (C-243/Cm-244, Np-237, Pu-238, Pu-239/240) from the analysis. In addition, in Section 2.3.1, Open Land Area Soil Sampling and Scanning, HDI committed to submitting 10% of all soil samples offsite for analysis for the full suite of radionuclides.
Holtec Response The plan for the characterization campaign that generated the results summarized in the Oyster Creek Generating Station Radiological Characterization Report and included as Enclosure 5 to the Oyster Creek License Termination Plan (LTP) submittal specified that 10% of all soil samples would be analyzed for the full suite of 21 radionuclides of concern (ROCs) identified in Enclosure 4 of the LTP submittal, Radionuclide Selection for DCGL Development Oyster Creek Station Site Characterization Project. Upon mobilization to the field to perform characterization, this approach was modified based on site-specific conditions and contamination likelihood. Ten percent of the samples were sent to an off-site laboratory for a more focused suite of HTD analysis, relying on a decision-logic-based approach in areas where lower contamination potential existed. Site-wide presence of all 21 ROCs was not expected based on information in the Historical Site Assessment (HSA). All designated Quality Control (QC) samples were analyzed for Sr-90, C-14, Fe-55, Ni-63, and Tc-99. Pu-241 was included in the HTD analyses for QC samples collected in the NPA, SPA, and RCA; that is, the survey areas having the highest potential for transuranic contamination. In areas with known contamination, Co-60, Cs-137, and Sr-90 were used as indicators for broader groups of HTDs based on their correlation with other radionuclides.
This decision was made to avoid redundant sampling in areas with a lower likelihood of HTD presence and to focus on higher-risk areas. However, this targeted approach provided sufficient coverage to assess contamination levels and characterize radionuclide presence across the site.
Co-60 was used to indicate activation products such as Fe-55, Ni-63, and Tc-99.
Cs-137 and Sr-90 were used as indicators of other fission products, including Tc-99.
Pu-241 and Am-241 represented transuranics like Cm-243/244, Np-237, Pu-238, and Pu-239/240.
In the areas where HTD radionuclide contamination was less likely or where indicator radionuclides did not show significant activity, the full HTD suite analysis was not considered
5 necessary. This indicator-based approach allowed efficient assessment for contamination in areas of concern without conducting a full HTD suite for each sample.
Subsequent to the initial characterization campaign documented in the Oyster Creek Generating Station Characterization Report, additional characterization activities were performed in areas of concern identified in the HSA as having been potentially impacted by historical leaks and spills.
Technical Support Document 24-111, Soil Core Bores - Characterization Survey Plan for Oyster Creek Nuclear Generating Station, includes the plan for the additional focused surface and subsurface soil characterization campaign. The characterization campaign obtained samples of surface soil in addition to subsurface soil samples at incremental depths of up to 20 feet. Selected surface and subsurface soil samples were analyzed for the full suite of 21 Oyster Creek - specific ROCs. The results of the additional surface and subsurface soil analyses are summarized in Chapter 2 of Revision 1 of the Oyster Creek LTP.
As decommissioning activities progress, additional samples of soil and other impacted media will be collected as part of continuing characterization, remedial planning, or remedial action support surveys.
6 RSI-4, Oyster Creek Generating Station Site Radiological Characterization Report: Justify the selection of surface soil samples without easy to-detect (ETD) activity for HTD analysis, as these samples would not be expected to contain HTD radionuclides.
Rationale:
Several of the samples identified as having HTD analysis contained no ETD activity above the Minimum Detectable Concentration (MDC), despite several unselected samples having positive results for Cs-137 and/or Co-60. Generally, biased samples with the highest activity are selected for HTD analysis for determining radionuclide fractions, surrogate ratios and relative ratios. For example, RCA-DEP1-15-B (111 pCi/g Cobalt-60, 404 pCi/g Cesium-137), RCASEDI-3-B (1.1 pCi/g Cobalt-60, 14 pCi/g Cesium-137), RCA-SEDI-14-B (13.2 pCi/g Cobalt-60, 32.3 pCi/g Cesium-137), and RCA-SEDI-10-B (2.87 pCi/g Cobalt-60, 2.15 pCi/g Cesium-137) included no HTD analysis.
Holtec Response:
As the NRC staff pointed out in Oyster Creek RSI-8(c), Sr-90 is expected to be more mobile; therefore, the significant gamma emitting contributors may not be co-located with HTD radionuclides.
The samples in question were collected from the Radiologically Controlled Area (RCA), a Class 1 impacted area expected to undergo extensive remediation due to its historical contamination.
In most cases, the activity concentrations in the samples (e.g., RCA-DEP1-15-B, RCA-SEDI-3-B, RCA-SEDI-14-B, RCA-SEDI-10-B) exceed the Derived Concentration Guideline Levels (DCGLs) in Table 5-3 of the LTP, indicating that remediation is necessary. Given the planned remediation activities, the current radionuclide fractions and surrogate ratios derived from these surface soil samples may not remain valid after remediation and would likely not apply to other survey areas.
HTD analyses are resource-intensive and given the expected remediation-driven changes to the contamination profile, conducting detailed HTD analysis at this stage may not yield meaningful results for post-remediation conditions.
As described in the response to Oyster Creek RSI-3, additional characterization activities have been performed in areas of concern identified in the HSA as having been potentially impacted by historical leaks and spills. The characterization campaign obtained samples of surface soil in addition to subsurface soil samples at incremental depths of up to 20 feet. Selected surface and subsurface soil samples were analyzed for the full suite of 21 Oyster Creek - specific ROCs. The results of the additional surface and subsurface soil analyses are summarized in Chapter 2 of Revision 1 of the Oyster Creek LTP.
Post-remediation, Oyster Creek will reassess the need for detailed HTD analysis as part of the Final Status Survey (FSS) planning process, ensuring that the final site conditions are thoroughly assessed and compliant with release criteria.
7 RSI-5, Oyster Creek Generating Station Site Radiological Characterization Report:
Evaluate other contaminated media (e.g., pavement-covered areas and shallow concrete slabs, sediment, subsurface soils) for the full suite of radionuclides to establish radionuclide fractions and subsequent determination of insignificant contributors, surrogate ratios, and relative ratios.
Rationale:
Most of the samples having HTD results in the characterization report were from surface soils, with only two sediment and no subsurface and asphalt samples. Although there were sediment, asphalt, and subsurface samples exceeding the assessment criteria, these samples do not appear to be in the subset analyzed for HTDs.
Holtec Response:
During the initial Oyster Creek characterization performed in 2022 and described in the Oyster Creek Generating Station Site Characterization Report, the focus was primarily on surface soils, which are the most accessible media and provide an important baseline for contamination levels.
The depth profile for deep soil samples obtained during initial characterization was limited to 4 feet due to safety concerns and resistance that made the hand-AUGER sampling method impractical. In 2025, additional soil samples were obtained, including subsurface samples to depths of up to 20 feet.
Most of the "other contaminated media" samples (sediment, asphalt, and subsurface soils) were collected from the Radiologically Controlled Area (RCA), North Protected Area (NPA), and South Protected Area (SPA). Roof gravel samples were obtained from buildings that will remain following demolition activities.
Pavement-covered areas and shallow concrete slabs will be used during decommissioning activities for equipment laydown and demolition support, in addition to waste and backfill material sorting, staging and survey. Pavement and hard-facing material such as sidewalks will be removed as required to expose underlying soils for scanning and direct measurement.
Contaminated shallow concrete slabs and equipment pads will be removed consistent with the Oyster Creek demolition strategy. The radiological characteristics of concrete and asphalt are subject to change due to impacts from the ongoing demolition process. The bulk of this media will ultimately become radioactive waste, precluding the need to perform analyses for the full suite of potential radionuclides of concern (ROCs). Any surface or subsurface media that remains following decommissioning activities will be subject to FSS, including sampling and, where applicable, full suite analyses.
Roof gravel media was subject to impact from particulate radiological effluents and foot traffic and is very unlikely to contain hard-to-detect (HTD) radionuclides. The determination of the need for HTD analyses of this media will be made at the time of Final Status Survey of the building surfaces.
Sediment samples were biased toward areas with the potential for impact from historical plant operation, and included dry sediment from storm drain catchment areas, in most cases obtained above asphalt layers. Wet sediment samples were obtained from the bottom of the plant discharge canal (DCA). These samples validated Historical Site Assessment (HSA) conclusions concerning potential radiological impacts and informed the scope of continuing characterization, including the need for future HTD analyses.
8 As described in the response to RSI-3, additional characterization activities have been performed in areas of concern identified in the HSA as having been potentially impacted by historical leaks and spills. Technical Support Document 24-111, Soil Core Bores - Characterization Survey Plan for Oyster Creek Nuclear Generating Station, includes the plan for the additional focused surface and subsurface soil characterization campaign. The characterization campaign obtained samples of surface soil in addition to subsurface soil samples at incremental depths of up to 20 feet.
Selected surface and subsurface soil samples were analyzed for the full suite of 21 Oyster Creek
- specific ROCs. The results of the additional surface and subsurface soil analyses are summarized in Chapter 2 of Revision 1 of the Oyster Creek LTP.
HDI has concluded that the analyses of subgrade concrete represent the most comprehensive, representative and conservative approach for the evaluation of the relative impact of the 21 Oyster Creek ROCs. TSD 25-032 Radionuclides of Concern in Support of the Oyster Creek Station License Termination Plan, which is included with the Oyster Creek LTP Revision 1 submittal, evaluates the results of concrete samples that were analyzed for the 21 radionuclides in the initial suite of radionuclides of concern (ROCs) identified in Technical Basis Document (TBD) 20-6002-1362, Radionuclide Selection for DCGL Development Oyster Creek Station Site Characterization Project, which is included with the Oyster Creek LTP Revision 1 submittal as Enclosure 4. TSD 25-032 refines the initial ROCs into a final set of radionuclides of concern for use during final status survey (FSS). Radionuclide mixture fractions are established for the initial ROCs, and the results are used to eliminate some radionuclides as insignificant contributors (IC) to dose.
Additionally, surrogate ratios were determined for the hard-to-detect ROCs.
Continuing characterization will be performed as restrictions related to accessibility and background levels are eliminated and potential contamination from demolition and waste hauling activities are identified and investigated.
9 RSI-6, Oyster Creek Nuclear Generating Station Below Grade Structures Radiological Characterization Report: Provide measured activity, uncertainty, and the MDC for all radionuclide analyses conducted on each sample, including those with results less than the MDC to support the staffs review of the radionuclide fractions, insignificant contributors, surrogate ratios, and relative ratios.
Rationale:
The information provided in the LTP and the Oyster Creek Nuclear Generation Station Below Grade Structures Radiological Characterization Report did not provide the measured activity and uncertainty, nor the MDC, for HTD or gamma emitting radionuclides analyses other than Co-60 and Cs-137. The results were presented based on the percentage of the AC and only included if at least one sample exceeded the MDC.
HDI Response:
Oyster Creek will make available for NRC staff review a tabularized table of ETD and HTD results presented in the Oyster Creek Nuclear Generating Station Below Grade Structures Radiological Characterization Report.
10 RSI-7 OC LTP & Enclosure 6, Oyster Creek Nuclear Generating Station Below Grade Structures Radiological Characterization Report: Samples selected for HTD analysis should include the full suite of radionuclides in Table 2-7.
Rationale:
For below grade structures, samples selected for HTD analysis were not analyzed for the full suite of radionuclides. Rather, a decision logic tree (Enclosure 6, Table 3-1) was used to determine which samples were monitored for what radionuclides. The staff was not able to determine which samples were analyzed for the full suite of radionuclides in Table 2-7 of the OC LTP.
HDI Response:
The characterization campaign documented in the Oyster Creek Nuclear Generating Station Below Grade Structures Radiological Characterization Report produced a total of 139 concrete cores from subgrade structure floor and walls. The cores were segmented into 857 samples and analyzed for the presence of radionuclides of concern (ROCs)
Analyses for the full suite of the 21 Oyster Creek radionuclides of concern (ROCs) identified in the Radionuclide Selection for DCGL Development Oyster Creek Station Site Characterization Project report were conducted on a portion of the 857 samples. The tabularized table of ETD and HTD results developed in response to RSI-6 presents the results of the analyses of the concrete cores.
The analytical results from the concrete characterization campaign were used in the development of Technical Support Document (TSD) No.25-032, Radionuclides of Concern in Support of the Oyster Creek Station License Termination Plan, which is included with Oyster Creek License Termination Revision 1 submittal as Enclosure 18.
TSD 25-032 evaluates the results of a subset of the concrete samples that were analyzed for the full suite of OCNGS ROCs. TSD 25-032 refines the initial ROCs into a final set of radionuclides of concern for use during final status survey (FSS). Radionuclide mixture fractions are established for the initial ROCs, and the results are used to eliminate some radionuclides as insignificant contributors (IC) to dose. Additionally, surrogate ratios were determined for the hard-to-detect ROCs.
A tabular summary of the concrete characterization results is presented in LTP Revision 1 Chapter
- 2. In order to facilitate Staff review of the results of the concrete characterization, Oyster Creek will make the database containing the details of the analytical results, including minimum detectable activity and sensitivity results, available for Staff review.
11 RSI-8 Insignificant Contributors: Provide representative (additional) RCA sample data by area and media to support the determination of radionuclide fractions and the subsequent evaluation of insignificant contributors based on this data. Explain what further investigations were or will be conducted to determine the horizontal and vertical extent of the Sr-90 contamination in the RCA.
Rationale, Radionuclide Selection for DCGL Development Oyster Creek Station Site Characterization Project, and Enclosure 18, Dose Contribution from Insignificant Radionuclides in the Oyster Creek Site-Specific Suite of Radiological Nuclides, described the evaluation for insignificant contributor determination. Several concerns were identified:
(a) Enclosure 4: The dose contributions for Silver-108m, Barium-133, Hafnium-178m, Manganese-53, Niobium-92m, Lead-205, Promethium-145, Samarium-146, and Terbium-158, which are not available in the Decontamination and Decommissioning (DandD) code, were evaluated using the inhalation, ingestion, and direct exposures in Federal Guidance Report No. 11,Limiting Values of Radionuclide Intake and Air Concentration and Dose Conversion Factors for Inhalation, Submersion, and Ingestion, and Federal Guidance Report No.12, External Exposure to Radionuclides In Air, Water, and Soil. The dose conversion factors for the individual radionuclides were ratioed to that of Co-60 and multiplied by the dose result for Co-60 for each of the scenarios; however, justification was not provided to demonstrate that Co-60 would be sufficiently representative of the radiological and environmental properties of these radionuclides.
(b) Enclosure 18: The licensee collected five biased soil samples from the RCA for analysis of HTD radionuclides. From these samples, HDI concluded that the HTDs collectively contributed less than 10% of the dose criterion and could therefore be eliminated from further detailed analysis. However, to determine the magnitude and extent of residual radioactivity, a sufficient number of samples is required to capture statistical variability in the data by areas and media. Five RCA soil samples does not represent a sufficient sample number, nor has it been demonstrated that these samples are representative of all open land areas, building structures, and embedded and buried piping.
(c) Enclosure 18: Sr-90 was detected above the MDC in one of five samples used for the insignificant contributor analysis in Enclosure 18. Sr-90 is expected to be more mobile; therefore, the significant gamma emitting contributors may not be co-located with HTD radionuclides. Additional data across multiple media would be needed to support HDIs determination that Sr-90 is insignificant.
(d) Section 3.3 of NUREG-1757, Volume 2, Rev. 2, indicates that less likely but plausible (LLBP) exposure scenarios be considered when determining insignificant radionuclides and exposure pathways. Therefore, analyses of LLBP exposure scenarios should be considered when determining whether a radionuclide or pathway is insignificant and can be removed from detailed analysis (i.e., if a radionuclide is significant to dose for a LLBP exposure scenario such as the resident gardener scenario, then the radionuclide should be analyzed for in Final Status Survey (FSS) and in detailed dose analysis; this does not preclude use of surrogate ratios for HTD radionuclides that are important to dose for LLBP exposure scenarios if approved by the NRC). See also RSI-9 requesting information on LLBP exposure scenarios.
HDI has reconsidered the methodology for evaluation of insignificant radionuclides and concluded that the results of subgrade concrete characterization presented in RSI-6 represent the most
12 comprehensive and representative data appropriate for evaluation of Oyster Creek radionuclides of concern, radionuclide ratios, and insignificant dose contributors.
License Termination Plan Enclosure 6, Oyster Creek Nuclear Generating Station Below Grade Structures Radiological Characterization Report, documents the concrete characterization campaign performed to identify the nature and extent of radiological contamination in several Oyster Creek subgrade structures that will remain in place following decommissioning activities.
The analytical results from the concrete characterization campaign were used in the development of Technical Support Document (TSD) No.25-032, Radionuclides of Concern in Support of the Oyster Creek Station License Termination Plan, which is included with Oyster Creek License Termination Revision 1 submittal as Enclosure X.
As documented in the response to RSI-3, additional characterization activities to determine the horizontal and vertical extent of contamination were performed in areas of concern identified in the HSA as having been potentially impacted by historical leaks and spills. Technical Support Document 24-111, Soil Core Bores - Characterization Survey Plan for Oyster Creek Nuclear Generating Station, includes the plan for the additional focused surface and subsurface soil characterization campaign. The characterization campaign obtained samples of surface soil in addition to subsurface soil samples at incremental depths of up to 20 feet. Selected surface and subsurface soil samples were analyzed for the full suite of 21 Oyster Creek - specific ROCs. The results of the additional surface and subsurface soil analyses are summarized in Chapter 2 of Revision 1 of the Oyster Creek LTP.
Additional horizontal and vertical extent of contamination will be performed as necessary to plan radiological remediation. Remedial action support surveys will be performed to determine the adequacy of remediation and prepare for Final Status Survey. Continuing characterization will be performed as restrictions related to accessibility and background levels are eliminated and potential contamination from demolition and waste hauling activities are identified and investigated. Post-remediation, Oyster Creek will reassess the need for detailed HTD analysis as part of the Final Status Survey (FSS) planning process, ensuring that the final site conditions are thoroughly assessed and compliant with release criteria.
HDI has evaluated the additional concerns identified in Rationale items 8(a) through 8(d) associated with RSI-8 and offers the following clarifications:
Rationale 8(a)
Co-60 represented over 99% of the total dose in the resident farmer and building occupancy scenarios. Given Co-60s significant contribution and its role as an activation product, it is an appropriate proxy for other radionuclides unavailable in the DandD code. Most of the radionuclides in question, except Ba-133 and Sm-146, share similar properties with Co-60, decaying through electron capture or internal transition, and are expected to contribute minimally to the overall dose. While Ba-133 is a fission product, its low dose constant compared to Cs-137 supports its limited impact on overall dose calculations. Given Co-60s dominant contribution to dose, it was used as an indicator radionuclide for calculating the dose contributions of these other radionuclides, and this approach remains technically sound based on current modeling.
Rationale 8(b)
Oyster Creek LTP Chapter 2 presents the results of extensive concrete characterization of subgrade structures including the results of full suite analyses for many of the wall and floor samples obtained at various depths.
13 TSD 25-032 evaluates the results of concrete samples that were analyzed for the 21 radionuclides in the initial suite of radionuclides of concern (ROCs) identified in Technical Basis Document (TBD) 20-6002-1362, Radionuclide Selection for DCGL Development Oyster Creek Station Site Characterization Project. TSD 25-032 refines the initial ROCs into a final set of radionuclides of concern for use during final status survey (FSS). Radionuclide mixture fractions are established for the initial ROCs, and the results are used to eliminate some radionuclides as insignificant contributors (IC) to dose. Additionally, surrogate ratios were determined for the hard-to-detect ROCs.
Rationale 8(c)
HDI has concluded that the analyses of subgrade concrete represent the most comprehensive, representative and conservative approach for the evaluation of the relative impact of the 21 Oyster Creek ROCs, including Sr-90.
Rationale 8 (d)
As described in the HDI response to RSI-8(a), RSI-8(b) and RSI8(c) above, HDI has concluded that the analyses of subgrade concrete for the 21 Oyster Creek radionuclides of concern represent the most comprehensive, representative and conservative approach for the evaluation of significant and insignificant dose contributors. The nuclide fractions and insignificant contributors will be used in the evaluation of the dose consequences of Less Likely But Plausible scenarios documented in the response to RSI-9.
14 RSI-9 Provide the LLBP exposure scenario results outlined in the OCNGS LTP to support the staff's risk informed decision making. HDI has chosen the industrial scenario for its assessment, assumes the soil may be arable, deselected specific radionuclides, and eliminated the groundwater pathway from the dose assessment within the industrial scenario. HDIs analysis should demonstrate that the radionuclide or pathway must be insignificant for all exposure scenarios considered (e.g., residential scenarios as well as the proposed industrial scenario) in order to justify the use of the industrial scenario.
Rationale:
The LLBP analysis is used to risk-inform the decision about the industrial scenario selection. As explained in NUREG-1757, Vol 2, Rev. 2, If the licensee bases its compliance exposure scenario on reasonably foreseeable land use scenarios which are not clearly bounding, the licensee should also identify LLBP land use scenarios. These are scenarios that could lead to higher doses compared to the reasonably foreseeable land use scenario used to demonstrate compliance with the LTR (license termination rule) criteria. The evaluation of LLBP exposure scenarios ensures that, if land uses other than the reasonably foreseeable land use were to occur in the future, unacceptably high risks would not result.
HDI Response to RSI-9 The compliance scenario selected for the OCNGS site is an Industrial Use (IU) scenario. In addition to the compliance scenario, HDI also evaluated the potential impact of two less likely but plausible (LLBP) exposure scenarios: Residential and Recreational. Due to possessing fewer open pathways, the recreational scenario is bounded by the residential scenario. The residential scenario is evaluated to determine the potential dose impact on a critical receptor 30 years after license termination, resulting from a future change in land-use for the OCNGS site.
For each dose-significant radionuclide of concern (ROC), doses under the IU scenario resulting from an initial soil concentration of 1 pCi/g were calculated across all media, summed, and scaled using the NRCs 25 mrem/year criterion for unrestricted release. The resulting soil concentrations were decay-adjusted assuming a 30 year period between license termination and possible transition to a residential LLBP land use.
As shown in LTP Table 6-4, comparing the decay-adjusted concentrations to the dose-equivalent concentrations under the LLBP Residential scenario demonstrates that, if the OCNGS site were to be released at soil concentrations meeting the 25 mrem/year limit under the IU scenario, the residual soil concentrations would meet the unrestricted use criteria under the LLBP Residential scenario 30 years later.
In addition to this evaluation, HDI assessed a hypothetical open drinking water pathway using untreated site groundwater as the drinking water source under the IU scenario. Although this scenario is extremely unlikely, it was conservatively evaluated to support the risk-informed decision further. The analysis shows that, even with the addition of an onsite well as the source for drinking water, there is no significant impact on dose to a hypothetical receptor. This conclusion is supported by the following:
Tritium is the only radionuclide detected in OCNGS groundwater over several decades of monitoring;
15 While tritium is mobile, its contribution to dose under any plausible drinking water exposure scenario is negligible; Other ROCs have not been detected in groundwater or are considered immobile and unlikely to migrate to receptor points.
In summary, HDIs evaluation demonstrates that the selected Industrial Use scenario is both reasonable and bounding in comparison to LLBP scenarios, including residential use and use of site groundwater as a drinking water source.